使用消息队列处理串口接收，出现线程卡住的问题

发布于 2022-08-16 20:07:19 浏览：1550 订阅该版

代码如下，串口中断里面发送消息，在serial_thread_entry线程里面接收，发现数据量比较大的时候，中断uart_input里面报消息队列满了之后，`result = rt_mq_recv(rx_mq, (void*)&msg, sizeof(msg), 5);`会一直卡在这里面，设置了超时也没有任何作用，是不是系统的bug?

```c
#include <rtthread.h>
//#include <board.h>
#include <rtdevice.h>

//#include "debug_pin.h"
#define SAMPLE_UART_NAME       "uart2"      /* 串口设备名称 */
#define BUF_SIZE				(256)
/* 串口接收消息结构*/
struct rx_msg
{
    //rt_device_t dev;
    //rt_size_t size;
	char buffer[BUF_SIZE + 1];
	rt_size_t size;
};
/* 串口设备句柄 */
static rt_device_t serial;
/* 消息队列控制块 */
static struct rt_messagequeue* rx_mq;

/* 接收数据回调函数 */
static rt_err_t uart_input(rt_device_t dev, rt_size_t size)
{
    struct rx_msg msg;
    rt_err_t result;
    //msg.dev = dev;
    //msg.size = size;
	msg.size = rt_device_read(dev, 0, msg.buffer, BUF_SIZE);
    result = rt_mq_send(rx_mq, (void*)&msg, sizeof(msg));
	rt_kprintf("mlen %d\n", size);
    if ( result == -RT_EFULL)
    {
        /* 消息队列满 */
        rt_kprintf("message queue full!\n");
    }
    return result;
}

static void serial_thread_entry(void *parameter)
{
    struct rx_msg msg;
    rt_err_t result;
    //rt_uint32_t rx_length;
    //static char rx_buffer[BUF_SIZE + 1];
	rt_kprintf("start serial thread\n");
    while (1)
    {
        rt_memset(&msg, 0, sizeof(msg));
        /* 从消息队列中读取消息*/
        result = rt_mq_recv(rx_mq, (void*)&msg, sizeof(msg), 5);//RT_WAITING_FOREVER);
        if (result == RT_EOK)
        {
            /* 从串口读取数据*/
            //rx_length = rt_device_read(msg.dev, 0, rx_buffer, msg.size);
            //rx_buffer[rx_length] = '\0';
			msg.buffer[msg.size] = '\0';
            /* 通过串口设备 serial 输出读取到的消息 */
			//debug_pin_on();
            //rt_device_write(serial, 0, rx_buffer, rx_length);
			rt_device_write(serial, 0, msg.buffer, msg.size);
			//debug_pin_off();
            /* 打印数据 */
            rt_kprintf("%s\n",msg.buffer);
        }
    }
}

static rt_err_t uart_tx_finish(rt_device_t dev, void *buffer)
{
	rt_kprintf("message tx finish!\n");
	return RT_EOK;
}

int uart_dma_sample(void)
{
    rt_err_t ret = RT_EOK;
    char uart_name[RT_NAME_MAX];

char str[] = "hello RT-Thread!\r\n";
	struct serial_configure config = RT_SERIAL_CONFIG_DEFAULT;
  
    rt_strncpy(uart_name, SAMPLE_UART_NAME, RT_NAME_MAX);

/* 查找串口设备 */
    serial = rt_device_find(uart_name);
    if (!serial)
    {
        rt_kprintf("find %s failed!\n", uart_name);
        return RT_ERROR;
    }

/* 初始化消息队列 */
    rx_mq = rt_mq_create("rx_mq", sizeof(struct rx_msg), 3, RT_IPC_FLAG_PRIO);

config.baud_rate = BAUD_RATE_115200;       
	config.data_bits = DATA_BITS_8;           
	config.stop_bits = STOP_BITS_1;           
	config.bufsz     = BUF_SIZE;                   
	config.parity    = PARITY_NONE;

rt_device_control(serial, RT_DEVICE_CTRL_CONFIG, &config);

/* 以 DMA 接收及轮询发送方式打开串口设备 */
    rt_device_open(serial, RT_DEVICE_FLAG_DMA_RX|RT_DEVICE_FLAG_INT_TX);//RT_DEVICE_FLAG_DMA_RX);
    /* 设置接收回调函数 */
    rt_device_set_rx_indicate(serial, uart_input);
	rt_device_set_tx_complete(serial, uart_tx_finish);
    /* 发送字符串 */
    rt_device_write(serial, 0, str, (sizeof(str) - 1));

/* 创建 serial 线程 */
    rt_thread_t thread = rt_thread_create("serial", serial_thread_entry, RT_NULL, 1024, 25, 10);
    /* 创建成功则启动线程 */
    if (thread != RT_NULL)
    {
        rt_thread_startup(thread);
    }
    else
    {
        ret = RT_ERROR;
    }

return ret;
}
/* 导出到 msh 命令列表中 */
MSH_CMD_EXPORT(uart_dma_sample, uart device dma sample);

void uart_task(void)
{
	uart_dma_sample();
}
```